[EM] Nightmare On IRV Street ?

[Dave Ketchum]

On Fri, 4 Jul 2003 18:34:51 EDT Dgamble997 at aol.com wrote:

 >
 > Firstly my example, yes Adam and Kevin your analysis is correct. A
 > casting a second preference for B serves only to defeat C and elect B
 > and vice versa.
 >
 > The collective result however of these two strategies under Condorcet is
 > that neither A  or C supporters get their first choice. If both A and C
 > express a single preference each has a 50% chance of getting their first
 > choice. As it is B wins with 14% support under Condorcet.


Said another way, if the A supporters "express a single preference", C
rather than B will win if A does not - BUT they should have voted this way
originally if this was their desire.  Note that this possible action by A
supporters does not improve the chance of A winning - it only changes the
effect of A losing.  C supporters have a similar option.

 >
 > Adam Tarr wrote
 >
 > Can you really put the Condorcet "nighmare" scenario I wrote in the same
 > ballpark as the IRV nightmare scenario?  My Condorcet scenario ends with
 > the compromise candidate winning, and nobody regretting their vote.  In the
 > IRV scenario I showed, the clearly, indisputably pre-eminent candidate
 > loses, and a third of the electorate is kicking themselves on election
 > night.
 >
 >
 > No I don't put the Condorcet "nightmare" in the same ballpark as the IRV
 > "nightmare" I feel it is worse. I am not at all happy- for all sorts of
 > "turkey" reasons explored extensively in previous posts-  with  any
 > single member system that can elect  candidates with a low first
 > preference vote. I see your nightmare IRV scenario as an acceptable
 > scenario which could occur in a close race where the electorate is
 > divided into three approximately equal factions- no method is perfect
 > and elections will sometimes be close.
 >
 > Adam also wrote
 >
 > That's a pretty big non sequitur there.  Why IRV?  Simply because that's
 > what the largest US electoral reform group supports?
 >
 > No not at all. I'm not prone to supporting things simply because certain
 > groups or people say so. My argument in favour of IRV is as follows:
 >
 > 1/ IRV prevents a minority winning an election because the majority
 > divides its support between 2 or more candidates.
 >
 > 2/ IRV ( compared to plurality) tends to elect moderate compromise
 > candidates who enjoy general support.
 >
 > But doesn't Condorcet do these things as well, in fact doesn't Condorcet
 > do these things much better ?
 >
 > The answer is of course yes. Condorcet does them better, Condorcet does
 > them too well. In a 3 party ( right, centre, left) election with no
 > absolute majority the centre candidate must come at least second to win
 > under IRV. Under Condorcet s/he could win from third.
 >
 > Considering this result in isolation from previous elections and the
 > possible outcome of future ones Condorcet seems to be the better method.
 >
 > Now to what could happen with Condorcet in practice. Condorcet favours
 > centrist candidates and parties, in my opinion to too great a degree.
 > Under Condorcet a centrist party would be very difficult to defeat.
 > Swapping the Democrat/Republican duopoly for a centrist monopoly would
 > not be good.  Effective one party states (like Mexico and India were for
 > decades) are generally a bad thing. Periodic change in government is
 > necessary for a healthy democracy. The Democrat/ Republican duopoly
 > bears testimony to the dangers of excessive stability and stagnation.


BUT, how does Condorcet favor centrist more than IRV?  They use identical
ballots and voting rules, each intending to elect the most popular
candidate.  We make much of the IRV horror stories which occur when IRV
selects a different candidate due to guessing that the parts of the
ballots it ignores will be consistent with what it reads; not due to any
desire for more or less favoring in any direction.  Look at:
       A - let's increase taxes for needed social spending.
       B - let's reduce taxes to reduce need for social spending.
       C - reduce taxes, concentrating on taxes on investments.
       D - reduce taxes, concentrating on taxes on wages.

And following votes:
       40 A
       19 B
       20 C>B
       21 D>B

IRV will see a desire to raise taxes; Condorcet a desire to reduce them.

Note that with a bit less support for C and/or D, IRV would have agreed
with Condorcet as to B.

 >
 > IRV appears to strike a balance between ensuring that a candidate
 > reflects the consensus and  enjoys general support and the alternation
 > of government necessary for a healthy democracy.
 >
 > David Gamble

-- 
davek at clarityconnect.com  http://www.clarityconnect.com/webpages3/davek
   Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
             Do to no one what you would not want done to you.
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